Manganese (Mn) is a potent neurotoxin. We hypothesize that PARK2, a strong Parkinson's disease (PD) genetic risk factor, alters neuronal vulnerability to modifiers of cellular Mn status, particularly at the level of mitochondrial dysfunction and oxidative stress. The long-term goal of this research is to elucidate the basis of Mn-induced neurotoxicity and to identify mechanistic-based neuroprotective strategies to mitigate human Mn exposure risk. Our approach will utilize a novel high-throughput assay of intracellular Mn levels to identify small molecule modifiers of cellular Mn status and neurotoxicity. Genetic modifiers of Mn transport and toxicity will be defined and translational studies of existing and newly identified genetic and small molecule modifiers of Mn toxicity will be performed utilizing a primary human neuronal model system based upon human induced pluripotent stem cell (hiPSC) technology. Aim 1 will identify lead compounds that alter neuronal Mn transport and toxicity in vitro using striatal and mesencephalic murine neuronal cell lines and in vivo using C. elegans. Aim 2 will delineate functional pathways that regulate Mn transport and toxicity in vivo and in vitro. Specific Aim 3 will test the hypothesis that human neuronal models of PD exhibit increased sensitivity to perturbations of cellular Mn status. These specific aims hold the promise of delineating common initiator signals for the modulation of Mn neurotoxicity, shedding light on mechanisms and susceptibility associated with exposure to this metal. This dual-PI proposal is bolstered by its use of innovative state-of-the-art complimentary approaches in diverse model systems.